Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>TTAS (#2) is good practice. "Lurking" and waiting for the "opportunity" before doing <code>CAS</code> is common practice in both Java and .NET concurrent classes. With that said, <code>cmpxchg</code> received quite a lot of optimizations in the last few years, so it might be possible that you'd get nearly identical results on the latest crop of processors.</p> <p>What you should try in both cases, however is to employ some <a href="http://www.cs.brown.edu/courses/cs176/ch07.ppt" rel="nofollow">exponential backoff</a> when you spin.</p> <p><strong>Update</strong></p> <p>@GJ: You should find <a href="http://software.intel.com/en-us/articles/implementing-scalable-atomic-locks-for-multi-core-intel-em64t-and-ia32-architectures/?wapkw=%28Implementing+Scalable+Atomic+Locks+Multi%29" rel="nofollow">some more up-to-date documentation on Intel's site</a>. Note the paragraph about not locking the bus since 486 and the comparison chart of <code>xchg</code> and <code>cmpxchg</code> that shows that they are practically identical. </p> <p>Spinning on a read vs on a <code>locked</code> instruction will still be a good idea to avoid some contention on getting the cache line in exclusive mode. (So TTAS.)</p> <p>However this will provide a useful gain only if you implement e.g. an exponential back-off, even yielding the CPU after a while. </p> <p>The differences between TTAS and TAS, or w/o backoff would be smaller if you are using a single, modern multi-core CPU with a shared L3 cache between the cores and would become more visible if you are using a multi-socket - e.g. server - machine or a multi-core CPU that has no shared cache between the cores. They would also be different based on the amount of contention. (I.e. light load would see smaller difference between TTAS/TAS.)</p>
    singulars
    1. This table or related slice is empty.
    1. POWhen to use Test&Set or Test&Test&Set?
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USAndras Vass
    1. USAndras Vass
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POWhen to use Test&Set or Test&Test&Set?
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTAcceptedByOriginator
    1. COTkanks for help, link is also very useful. :)
      singulars
      1. PO
      1. USGJ.
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload